Every agent turn starts with the model receiving context. In EONYX it is built from three mechanisms: AGENTS.md — the project’s persistent instructions, sessions — the full conversation history on disk, and auto-summarization — compaction of older turns once the history approaches the limit of the context window.

A skill is a folder with a SKILL.md file: an instruction the agent loads when a task matches it. Skills let you package repetitive procedures — a code review, a deploy checklist, the rules for formatting a report — so that they don’t take up context until they’re needed.

EONYX is written in Go and builds into a single static binary. Inside is a tidy set of packages built around one central abstraction. Let’s walk through how it is put together — useful both for contributors and for understanding the agent’s behaviour.

An agent that reads and edits code and runs commands must operate within explicit permissions. In EONYX security is several layers: a static gateway, a file sandbox, plan mode and a coarse block on dangerous commands. Let’s go through each of them.

The main way to work with EONYX is the interactive terminal interface (TUI): response streaming, the command palette, pickers and dialogs. Here is everything worth knowing to work fast.

A subagent is a separate instance of the agent that EONYX hands part of the work to. It performs the task in its own context window, with a reduced set of tools, and returns only the result into the main conversation. This keeps the main context clean: the details of the research don’t clutter the dialog. This article covers the task tool, the full list of built-in tools, and how the agent loop works.